Alter the logo on my Wordpress website

I have an existing website which we were using for our company and we have changed the company name. I can alter the text, photo's post etc but cannot replace the existing company logo or certain other bits which are as follows:

Replace existing logo with new one (top left corner)

Alter the green enquiry form to say 'If you have a project in mind, need legal advice or have a dispute to resolve get in touch'
There needs a box adding where potential customers can write a short message and
Alter the footer as follows:
Remove the two Houzz links
Remove the red 'Master Builders' logo
Change the address box remove '(c)Project Home Ltd' and replace it with Speak & Mortlock
Remove the 'Company Reg' reference

New Logo below